This should contain the introduction from the documentation isn't it? I thought I read this in some discussion.

"The `BlockBundle`_ provides integration with SonataBlockBundle. It assists you
in managing fragments of contents, so-called blocks. What the BlockBundle does
is similar to what Twig does, but for blocks that are persisted in a DB.
Thus, the blocks can be made editable for an editor.  Also the BlockBundle
provides the logic to determine which block should be rendered on which pages."